1. Technical Field
The present invention relates to switch assemblies. In particular, it relates to a sealed switch assembly for use in environments exposed to fluids and a method of repairing the switches such that the seals remain intact after replacement.
2. Background Art
Recent advances in the medical arts, particularly in the field of surgery, have resulted in the development of a variety of sophisticated high technology instruments. Many of these devices include a variety of manual switch assemblies designed to allow a surgeon to activate particular functions while operating on a patient. One group of such instruments includes laparoscopic, colonoscopic, gastroscopic, and other surgical devices designed to be manipulated by a surgeon working through small apertures in the body wall of the patient, or in body cavity openings, during surgery. For ease of discussion, any of these or other devices shall be referred to by the single term: xe2x80x9claparoscopicxe2x80x9d device, with the understanding that, as used herein, the term laparoscopic device is intended to cover any device capable of using the subject matter of this invention. It is common when using laparoscopic surgical devices to have multiple switches arranged upon the handle of the device which allows a surgeon to perform multiple functions with a single hand.
Due to the nature of their use, laparoscopic surgical instruments require meticulous cleaning between uses. If the housing assembly which holds the switches is not properly sealed, the cleaning process itself may often create problems. For example, there may be damage to switches caused by cleaning fluids and/or contamination of the switch housing by the cleaning fluids. This can be caused by leakage of cleaning solutions into the switch housing which secures the switches.
The switch housing is normally designed to provide a tight external fluid seal which prevents entrance of fluids into the inside the switch housing, while simultaneously providing a flexible manually operable switch button which permits the surgeon to activate the switches on the switch housing. One method of providing the fluid seal has been to secure the switches to apertures on the switch housing such that they can be activated from the outside of the housing by the surgeon, and to seal the switch housing assembly by covering the aperture and the switch with a flexible switch button which is adhered to the outer surface of the switch housing. This causes a common problem related to laparoscopic surgical instruments, as well as other instruments which use switches that are sealed by flexible switch buttons. The prior art methods of glueing the switch buttons to the exterior of the switch housing assembly requires an excessive amount of work in order to replace the flexible switch button when the switch button is damaged. In order to prepare the surface of the switch housing assembly such that a replacement switch button can be properly secured to it, a substantial amount of time must be spent to ensure that any pre-existing adhesive is removed prior to application of a new cover with fresh adhesive. Failure to do so may result in unwanted leakage points which would allow unwanted fluid flows created during surgery, or cleaning fluids used after the surgery, to enter the device. It would be desirable to have a method of rapidly sealing a switch button to a switch housing assembly, without adhesive, such that no fluid leaks exist between the switch button and the switch housing assembly.
Another attempt to ensure that the seal is maintained in proper working order has been to secure the switch and the switch button from the inside of the housing assembly. This is typically done by securing the switch and the switch button from the inside of the housing and then filling the housing with a material, such as resin, to prevent both the switch and the switch button from moving. This process creates an additional drawback in that the resin, once set, is usually not removable. Therefore, when the seal is broken, the entire switch housing must be discarded and replaced. Due to the fact that these switch assemblies are precision devices, the cost of total replacement of the switch assembly is higher then desired.
Another disadvantage related to current switch housing assemblies used on laparoscopic surgical instruments is the method by which the switches are secured to the switch housing assembly. Prior art devices typically secure the switch to the switch housing assembly and then ensure that it does not move by filling the interior of the switch housing assembly with material such as.resin, epoxy, etc. The disadvantage to this method of securing the switches is that it is extremely difficult to remove the resin if the switch assembly needs repair. As a result, if any of the switches or switch buttons become defective, a common repair procedure is to discard the entire switch housing assembly, along with all of the switches and switch buttons, and to replace them entirely. It would be desirable to be able to minimize costs by replacing, in a rapid and convenient manner, only those components which are actually defective.
While addressing the basic desirability of using flexible switch buttons to provide access to switches inside a switch housing while maintaining a fluid seal, the prior art has failed to provide a switch housing assembly which is inexpensive to manufacture, has a minimum number of components, and can be repaired without with a minimum amount of time and with minimum replacement parts costs.
The present invention solves the foregoing problems by providing a switch housing assembly which uses an internal pressure bracket to simultaneously secure multiple switches to multiple locations within the switch housing assembly. One or more switches each secure a flexible fluid sealing switch button to the inside of the switch housing by applying pressure directly from the switch body against the switch button. In turn, the switches are simultaneously secured to the switch buttons by the internal bracket which simultaneously provides pressure against the backs of one or more switches. The bracket assembly is preferably secured to the switch housing by a single removable screw which allows disassembly when needed. Optionally, the securing screw has a female threaded aperture to allow a second screw to secure the switch housing to the body of the laparoscopic surgical instrument.